1. Field of the Invention
The present invention relates to an apparatus to adjust the head gap of an ink-jet printer. More specifically, the present invention relates to an apparatus to adjust the head gap of an ink-jet printer, in which the gap between the paper and a print head is simply and precisely adjusted in accordance with the thickness of the paper in a simple manner.
2. Description of the Related Art
Generally as shown in FIG. 1, an ink-jet printer includes: a print head 30 with a nozzle 31 formed on its bottom, to discharge the ink; a carrier 20 with the print head 30 installed thereon; and a chassis 10 to secure the both ends of a guide rail 11 and a carrier shaft 50 to guide the movement of the carrier 20.
The carrier 20 includes a rear supporting bracket 51 and a slider 22 so that the carrier 20 can move to left and right sides along the carrier shaft 50 and the guide rail 11.
Accordingly, when a paper 40 is picked up by a pickup roller (not illustrated) from a paper-feeding tray or a cassette and is passed through under the print head 30 through a feeding roller 60, the print head 30 moves to the left and the right along the carrier shaft 50 and the guide rail 11, and at the same time, discharges the ink through a nozzle 31, thereby carrying out the printing.
In this ink-jet printer, however, generally the distance between the paper 40 and the nozzle 31 of the bottom of the print head 30 is constantly fixed. Accordingly, in the case where a thick paper such as an envelope or a post card is printed, the distance between the paper and the nozzle 31 of the bottom of the print head 30 is reduced or becomes irregular.
In this case, the ink is spread astray, and therefore, the resolution of the printing is aggravated.
In order to solve this problem in the conventional ink-jet printer, a head gap adjusting apparatus 90 (See FIG. 2) is installed on each of both ends (only one end 50a is illustrated) of the carrier shaft 50 so that the distance (called “head gap” below) between the paper 40 and the head can be adjusted in accordance with the thickness of the paper.
The head gap adjusting apparatus 90 includes: a vertical hole 91 formed at a relevant position of the chassis 10, to receive one end 50a of the carrier shaft 50; an elastic spring 92 elastically supporting the one end 50a of the carrier shaft 50 within the hole 91 to prevent any loose movements of the end 50a of the carrier shaft 50 during the printing movements of the carrier 20; and a head gap adjusting plate 93 movably securing the end 50a of the carrier shaft 50 within the vertical hole 91 to make the end 50a of the carrier shaft 50 move up and down against the elastic force of the spring 92, so as to adjust the head gap.
One end 92a of the elastic spring 92 is supported at a first supporting protuberance 16 of the chassis 10 and is inserted into a supporting hole 14. Another end 92b of the elastic spring 92 is supported at a second supporting protuberance 18 of the chassis 10 so as to press an end 50a of the carrier shaft 50 to a position below the vertical hole 91.
The head gap adjusting plate 93 includes: a rotation shaft 94 formed on the lower portion of the head gap adjusting plate 93, to make it possible for the head gap adjusting plate 93 to pivot over the chassis 10; a spiral cam hole 95 to move the end 50a of the carrier shaft 50 up and down against the elastic forces of the elastic spring 92 during the pivoting of the head gap adjusting plate 93 around the rotation shaft 94; a saw tooth part 96 to adjust the pivoting of the head gap adjusting plate 93 in cooperation with an adjusting protuberance 19 of the chassis 10; a screw part 98 fastened to a screw hole (not illustrated) of the chassis 10, to fix the head gap adjusting plate 93 to the adjusted position after the head gap adjusting plate 93 is adjusted to the desired position through the saw tooth part 96 by pivoting the head gap adjusting plate 93; and a knob 99 to pivot the head gap adjusting plate 93.
This head gap adjusting apparatus 90 will be described as to its operation below.
In the case where the head gap is expanded to print an envelope, a post card and the like, first the screw part 98 is loosened so that the head gap adjusting plate 93 can be pivoted around the rotation shaft 94 along a slide hole 97 in the direction of the arrow mark A or B.
After the screw part 98 is loosened, the head gap adjusting part 93 is pivoted with the knob 99 around the rotation shaft 94 along the slide hole 97 in the direction of the arrow mark B. Accordingly, the spiral cam hole 95, which is inclined to have a level higher when positioned in the direction of the arrow mark A, moves in the direction of the arrow mark B, as shown in FIG. 2, so as to lift the end 50a of the carrier shaft 50.
At this time, the degree of pivoting the head gap adjusting plate 93 by the knob 99 is adjusted with the saw tooth part 96 and the adjusting protuberance 19.
Thus, when the head gap adjustment is completed through the pivoting of the head gap adjusting plate 93, the screw part 98 is tightened into the screw hole of the chassis 10 to fix the head gap adjusting plate 93 to the adjusted position.
On the other hand, in the case where the head gap is to be reduced to print a general size paper, i.e., 8.5′×11″ or A4, the head gap adjusting plate 93 is pivoted in a direction opposite to that which is described above, thereby lowering the carrier shaft 50 to the original position.
In this conventional head gap adjusting apparatus 90, however, to adjust the head gap, there is separately employed the head gap adjusting plate 93, which is very complicated.
Consequently, the number of the components is increased, which increases the manufacturing costs. Further, if the head gap is to be adjusted, the screw part 98, which has the head gap adjusting plate 93 securely fixed, has to be loosened, and the head gap adjusting plate 93 has to be adjusted by pivoting it, and then and, the screw part 98 has to be tightened. Thus the adjusting procedure is very complicated and troublesome.
Further, in this conventional head gap adjusting apparatus 90, the pivoting degree of the head gap adjusting plate 93 to adjust the head gap is determined by the saw tooth part 96 and the adjusting protuberance 19.
Accordingly, the saw tooth part 96 has to be designed to have a certain size large enough to maintain the head gap adjusting plate 93 at the adjusted position against the elastic force of the elastic spring 92. Therefore, fine adjustments to cater to various levels of paper thickness are impossible.